Has the licensing of respiratory quinolones for adults and the 7-valent pneumococcal conjugate vaccine (PCV-7) for children had herd effects with respect to antimicrobial non-susceptibility in invasive Streptococcus pneumoniae?

Abstract

The aim of the study was to analyse the evolution of antibiotic non-susceptibility in Spanish invasive Streptococcus pneumoniae after licensure of respiratory-quinolones for adults and 7-valent pneumococcal conjugate vaccine (PCV-7) for immunization of children. All invasive pneumococci received in the Reference Laboratory (January 2000-August 2007; n = 12 957 isolates) were serotyped, and susceptibility to penicillin/erythromycin/levofloxacin was determined. Antibiotic consumption and PCV-7 doses/year were provided by IMS and the manufacturer, respectively. In 2000-07, PCV-7 distribution (doses/1000 inhabitants </=59 months age/year) increased from 0.0 to 411.90, and antibiotic consumption (DDD/1000 inhabitants/day) was maintained for beta-lactams ( approximately 16), decreased for macrolides (from 4.4 to 2.7) and increased for respiratory fluoroquinolones (from 0.3 to 2.7). The increase in PCV-7 distribution correlated with a decrease in PCV-7 serotypes prevalence among invasive isolates in children (r = -0.976; P < 0.001) and adults (r = -0.905; P = 0.002). This decrease in PCV-7 serotypes correlated with a decrease in penicillin non-susceptibility in children (r = 0.929; P < 0.001) and adults (r = 0.905; P = 0.002) and with erythromycin non-susceptibility in children (r = 0.833; P = 0.010). Penicillin/erythromycin non-susceptibility in 2000 was significantly higher in paediatric versus adult isolates (penicillin: 51.4% versus 29.2%; erythromycin: 39.5% versus 20.4%), but similar in 2006-07 (20% to 24%). The increase in respiratory quinolones consumption correlated with the increase in levofloxacin non-susceptibility in adults (r = 0.926; P = 0.008) but not in children, with different non-susceptibility rates in 2007 (1.6% versus 0.0%; P = 0.013). This ecological analysis suggests that PCV-7 vaccination in children had a herd effect in adults, but consumption of respiratory quinolones in adults had no effect on pneumococcal susceptibility to levofloxacin in children. Penicillin/erythromycin non-susceptibility decreased along the studied period among paediatric invasive S. pneumoniae isolates to a level similar to that seen in adults.